07 yz450f fresh rebuild, can't start

1 reply to this topic
  • wiseone 910

Posted March 02, 2013 - 06:42 PM


I have a yz450f I just done the top end on, I put a new cylinder, piston, rings and went through the head and cleaned it up. I have fire, fuel, valve clearance is good, timing is good, the only thing is the compression test, I can't get a good reading because of the auto decompressor. What kind reading should I get, when I do compression test I get around 65-70 psi, on a leak down test I get 15-20 psi leakage on a fresh engine. I've tried starter fluid and I've kicked the shit out of it, and it will not even hit a lick, it won't do nothing, tried new plugs, set ex. Valves at .010''. Someone told me check the tps, could cause the bike not to hit at all? I need help I don't know what else to check other than electrical issues

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Krannie McKranface

Posted March 02, 2013 - 07:56 PM


Define 'done the top end'...........

Did you replace the valves?
Did you have the seats ground to match the new valves, and put in new guide seals?

65+ psi is normal with auto decompress.

..but how long does it last?

You should get zero leakage on a new engine....and where do you hear the leaking? I'll bet it's in the intake tract, from a leaky intake valve.

Related Content


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.